Timer to switch between 2 240v appliances on the same breaker

I was wondering if there is a timer that I could use to switch power between 2 30A 240v appliances. I am familiar with wiring just not able to find the missy part for my application. I have 2 30A appliances that I want to power with the same 50A breaker. I only want one on at a time switching every 12hours. Do you know of any such timers, all I'm able to find are timers to switch from on and off, I need one to switch from load A and load B. I hope I have made my self clear and concise. Thank you for your time.